Fan motor

ABSTRACT

An outer rotor fan motor includes a stator, a shaft that rotates about a central axis extending vertically, a bearing that supports the shaft to be rotatable with respect to the stator, and an impeller that is connected to the shaft via a shaft housing. The shaft includes a heat pipe extending in an axial direction. The shaft housing is connected to the shaft, extends in a radial direction, and is made of metal.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2018-217654 filed on Nov. 20, 2018, the entire contents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to an outer rotor fan motor.

BACKGROUND

In conventional motors, a heat pipe is embedded in a rotary shaft, and a rotor is provided on an outer peripheral portion of the rotary shaft. The rotary shaft protrudes from one end side of a housing and is configured as an output shaft. The heat pipe protrudes from the other end side of the housing and is provided with a plurality of heat dissipation fins. As a result, heat generated in the rotor can be transmitted from the heat pipe to the heat dissipation fins and released to the outside by the heat dissipation fins.

SUMMARY

An example embodiment of an outer rotor fan motor of the present disclosure includes a stator, a shaft that rotates about a central axis extending vertically, a bearing that supports the shaft to be rotatable with respect to the stator, and an impeller that is connected to the shaft via a shaft housing. The shaft includes a heat pipe extending in an axial direction. The shaft housing is connected to the shaft, extends in a radial direction, and is made of metal.

The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall perspective view of an example of a fan motor according to an example embodiment of the present disclosure.

FIG. 2 is a longitudinal sectional view of the fan motor.

FIG. 3 is a partial longitudinal sectional view of the fan motor.

FIG. 4 is a perspective view of a shaft housing and an impeller according to an example embodiment of the present disclosure.

FIG. 5 is a partial longitudinal sectional view of a fan motor according to a first modification of an example embodiment of the present disclosure.

FIG. 6 is a partial longitudinal sectional view of a fan motor according to a second modification of an example embodiment of the present disclosure.

FIG. 7 is a partial longitudinal sectional view of a fan motor according to a third modification of an example embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification, it is assumed that a direction in which a central axis of a fan motor extends is referred to simply as the term “axial direction”, “axial”, or “axially”, that directions perpendicular to the central axis of the fan motor and centered on the central axis are each referred to simply as the term “radial direction”, “radial”, or “radially”, and that a direction along a circular arc centered on the central axis of the fan motor is referred to simply as the term “circumferential direction”, “circumferential”, or “circumferentially”. In the present specification, it is also assumed that the axial direction is a vertical direction for the sake of convenience of the description, and shapes and positional relations of portions will be described on the assumption that the vertical direction in FIG. 2 is a vertical direction of the fan motor. An “upper side” of the fan motor is an “intake side”, and a “lower side” is an “exhaust side”. Note that the above definition of the vertical direction does not restrict the orientations and positional relations of the fan motor when in use. In the present specification, a section parallel to the axial direction is referred to as a “longitudinal section”. Note that the terms “parallel” and “perpendicular” used in the present specification include not only those “exactly parallel” and “exactly perpendicular”, respectively, but also those “substantially parallel” and “substantially perpendicular”, respectively.

FIG. 1 is an overall perspective view of an example of a fan motor 1 according to an example embodiment of the present disclosure. FIG. 2 is a longitudinal sectional view of the fan motor 1. FIG. 3 is a partial longitudinal sectional view of the fan motor 1.

The fan motor 1 is an outer rotor type fan motor. The fan motor 1 includes a housing 2, an impeller 3, and a motor 4. The motor 4 includes a shaft 41, a shaft housing 411, a rotor 42, a stator 51, and bearings 56. That is, the fan motor 1 according to the present example embodiment includes a stator 51, the shaft 41, the shaft housing 411, the bearing 56, and an impeller 3.

The housing 2 is arranged on the outer side of the impeller 3 and the motor 4. The housing 2 includes a housing tube portion 21 and rib portions 22.

The housing tube portion 21 is arranged on the radially outer side of the impeller 3. The housing tube portion 21 has a cylindrical shape that extends vertically in the axial direction. The impeller 3 and the motor 4 are accommodated in the housing tube portion 21. An intake port 221, which is a circular opening, is arranged at an axially upper end of the housing tube portion 21. An exhaust port 222, which is a circular opening, is arranged at an axially lower end of the housing tube portion 21.

The rib portion 22 is arranged on the radially inner side of the housing tube portion 21. The rib portion 22 is arranged at an axially lower portion of the housing tube portion 21 and is adjacent to the exhaust port 222. An outer end of the rib portion 22 in a direction perpendicular to the axial direction is connected to a radially inner surface of the housing tube portion 21. An inner end of the rib portion 22 in the direction perpendicular to the axial direction is connected to a radially outer surface of a base portion 53 to be described later. The rib portion 22 extends in the direction perpendicular to the axial direction and connects the housing tube portion 21 and the base portion 53. That is, the housing 2 supports the motor 4 via the rib portion 22. The plurality of rib portions 22 are arranged in the circumferential direction. Air flowing through the radially inner side of the housing tube portion 21 passes between the adjacent rib portions 22.

The impeller 3 is arranged on the radially inner side of the housing 2, that is, on the radially outer side of the motor 4. The impeller 3 is rotated about a central axis C by the motor 4. The impeller 3 includes an impeller cup 31 and a plurality of blades 32.

The impeller cup 31 is fixed to the motor 4. The impeller cup 31 is a substantially cylindrical member having an impeller lid portion 311 on the axially upper side. The shaft housing 411 of the motor 4 is connected to a radially inner end of the impeller lid portion 311. The impeller 3 is connected to the shaft 41 via the shaft housing 411. The rotor 42 of the motor 4 is fixed on the radially inner side of the impeller cup 31. The plurality of blades 32 are arranged in the circumferential direction on a radially outer surface of the impeller cup 31.

The motor 4 is arranged on the radially inner side of the housing 2. The motor 4 is supported by the housing 2 via the rib portion 22. The motor 4 rotates the impeller 3 about the central axis C. As described above, the motor 4 includes the shaft 41, the shaft housing 411, the rotor 42, the stator 51, and the bearing 56. The motor 4 further includes a cover member 52, a base portion 53, a circuit board 54, and a bearing holder 55.

The shaft 41 is arranged along the central axis C. The shaft 41 is a columnar member that is made of metal, for example, aluminum, stainless steel, or the like and extends vertically. The shaft 41 is supported by the bearing 56 so as to be rotatable about the central axis C. That is, the shaft 41 rotates about the central axis C extending vertically. The shaft housing 411 is connected to an axially upper end of the shaft 41. The impeller cup 31 is connected to a radially outer end of the shaft housing 411.

The rotor 42 is arranged on the radially outer side of the stator 51. The rotor 42 rotates about the central axis C with respect to the stator 51. The rotor 42 includes a rotor yoke 421 and a magnet 422.

The stator 51 is fixed to a radially outer surface of the tubular bearing holder 55 that holds the bearing 56. The stator 51 has an annular shape centered on the central axis C. The stator 51 opposes the rotor 42, which rotates about the vertically extending central axis C, in the radial direction. The stator 51 includes a stator core 511, and insulator 512, and a coil 513.

The stator core 511 is configured by vertically stacking electromagnetic steel plates, for example, silicon steel plates or the like. The stator core 511 is fixed to the radially outer surface of the bearing holder 55. The radially outer surface of the stator core 511 opposes a radially inner surface of the magnet 422 in the radial direction.

The insulator 512 is made of, for example, a resin having an insulating property. The insulator 512 is provided so as to surround an outer surface of the stator core 511. The coil 513 is configured using a conductive wire wound around the stator core 511 with the insulator 512 interposed therebetween. The conductive wire is electrically connected to the circuit board 54.

The cover member 52 is arranged on the axially upper side and the radially outer side of the stator 51. The cover member 52 of the present example embodiment accommodates at least an axially upper portion of the stator 51. More specifically, the stator 51 opposes the rotor 42 in the radial direction with the cover member 52 interposed therebetween. Note that there is also a case where the cover member 52 is not provided.

The base portion 53 is arranged at an axially lower end of the fan motor 1 on the axially lower side of the stator 51. The base portion 53 of the present example embodiment covers at least the axially lower side of the stator 51.

The circuit board 54 is arranged between the stator 51 and the base portion 53. That is, the circuit board 54 of the present example embodiment opposes the stator 51 and the base portion 53 in the axial direction. The circuit board 54 has, for example, a disk shape that extends in the radial direction with the central axis C as the center. The conductive wire of the coil 513 is electrically connected to the circuit board 54. An electric circuit configured to supply a drive current to the coil 513 is mounted on the circuit board 54.

The bearing holder 55 is arranged on the radially inner side of the stator 51 and the base portion 53. The bearing holder 55 has a cylindrical shape centered on the central axis C. An axially lower portion of the bearing holder 55 is fixed to the base portion 53. An axially upper end of the bearing holder 55 is located on the axially lower side of the shaft housing 411. The pair of the bearings 56 arranged vertically in the axial direction is accommodated and held on the radially inner side of the bearing holder 55. The stator core 511 is fixed to the radially outer surface of the bearing holder 55.

The bearing 56 is arranged on the radially inner side of the bearing holder 55. One side of the bearing 56 is arranged on the axially upper side of the stator 51. The other side of the bearing 56 is arranged on the axially lower side of the stator 51. The bearings 56 are, for example, a pair of upper and lower ball bearings in the axial direction. The bearing 56 supports the shaft 41 so as to be rotatable with respect to the stator 51.

When a drive current is supplied to the coil 513 of the stator 51 via the circuit board 54 in the fan motor 1 configured as described above, magnetic flux in the radial direction is generated in the stator core 511. As a magnetic field generated by the magnetic flux of the stator 51 and a magnetic field generated by the magnet 422 act on each other, torque is generated in the circumferential direction of the rotor 42. Due to this torque, the rotor 42 and the impeller 3 rotate about the central axis C. When the impeller 3 rotates, an air flow is generated by the plurality of blades 32. That is, in the fan motor 1, it is possible to generate and blow the air flow with the upper side as the intake side and the lower side as the exhaust side.

The shaft 41 includes a heat pipe 412 extending in the axial direction. The heat pipe 412 of the present example embodiment is embedded in the shaft 41. That is, the shaft 41 itself has the heat pipe structure.

The heat pipe 412 extends vertically in the axial direction from the axially lower side of the stator 51. An upper end of the heat pipe 412 is arranged at an axially upper end of the shaft 41, that is, at a connection portion 413 between the shaft 41 and the shaft housing 411. That is, the heat pipe 412 opposes the stator 51 in the radial direction over the entire area of the stator 51 in the axial direction.

The heat pipe 412 includes a small amount of hydraulic fluid and a wick (capillary structure) provided on an inner wall therein. When a portion close to the stator 51 (a high-temperature portion) of the heat pipe 412 is heated, the hydraulic fluid absorbs heat and evaporates. The hydraulic fluid vapor moves through an internal cavity of the heat pipe 412 to the shaft housing 411 side (a low-temperature portion). The hydraulic fluid vapor is cooled and condensed on the shaft housing 411 side (the low-temperature portion), returns to a liquid, and is absorbed by the wick. The hydraulic fluid absorbed by the wick moves to the stator 51 side (the high-temperature portion) by the capillary action of the wick. In this manner, the hydraulic fluid circulates inside the heat pipe 412, whereby heat moves from the stator 51 side (the high-temperature portion) to the shaft housing 411 side (the low-temperature portion).

The shaft housing 411 is connected to the radially outer surface of the axially upper end of the shaft 41. The shaft housing 411 is, for example, a disk-shaped metal member that extends in the radial direction with the central axis C as the center. That is, the shaft housing 411 of the present example embodiment is made of metal that is connected to the shaft 41 and extends in the radial direction. The connection portion 413 between the shaft 41 and the shaft housing 411 is arranged at the center of the shaft housing 411.

The shaft housing 411 is fitted into an opening 3111 provided in the impeller lid portion 311 of the impeller cup 31. The opening 3111 penetrates the impeller lid portion 311 vertically. The radially outer end of the shaft housing 411 is connected to the impeller lid portion 311.

According to the above configuration, the heat generated in the stator 51 is transmitted to the shaft housing 411 via the shaft 41 and the heat pipe 412. The shaft housing 411 is made of metal and has high thermal conductivity so that heat can be efficiently transmitted to one surface extending in the radial direction, and heat can be efficiently dissipated.

The rotation of the impeller 3 generates a flow of air on the surface of the shaft housing 411. In addition, the rotation of the shaft housing 411 also generates a flow from the center of the shaft housing 411 toward the radially outer side. These two air flows can improve heat dissipation characteristics.

Since the heat is dissipated by the shaft housing 411 connecting the shaft 41 and the impeller 3, it is unnecessary to provide a heat dissipation fin on the shaft 41 as in the related art. Thus, the fan motor 1 can be downsized. At this time, the fan motor 1 can be made smaller in the axial direction since the shaft housing 411 extending in the radial direction is fitted into the opening 3111 of the impeller lid portion 311 extending in the radial direction.

Since the bearing 56 is a ball bearing, sliding friction is small and heat generation is small. As a result, the bearing 56, which is the ball bearing, can keep the temperature of the bearing itself low and can prolong the service life.

A diameter D1 of the heat pipe 412 is equal to or longer than ½ of a diameter D2 of the shaft 41. As the diameter of the heat pipe 412 is larger, a heat transfer area increases, and the heat generated in the stator 51 can be transmitted to the heat pipe 412. As a result, it is possible to improve the heat dissipation characteristics.

An axial length L1 of the connection portion 413 between the shaft 41 and the shaft housing 411 is longer than the diameter D2 of the shaft 41. As the axial length L1 of the connection portion 413 is longer, a heat transfer area between the shaft 41 and the shaft housing 411 increases, and the heat generated in the stator 51 can be transmitted to the shaft housing 411. As a result, it is possible to improve the heat dissipation characteristics.

A diameter D3 of the shaft housing 411 is equal to or longer than twice the diameter D2 of the shaft 41. As the diameter of the shaft housing 411 is larger, a heat dissipation area to the outside air increases, and the heat generated in the stator 51 can be released into the air. As a result, it is possible to improve the heat dissipation characteristics.

The impeller 3 includes the impeller lid portion 311 that is connected to the shaft housing 411 and extends in the radial direction. The diameter D3 of the shaft housing 411 is equal to or longer than ½ of a diameter D4 of the impeller lid portion 311. As the diameter of the shaft housing 411 is larger, a heat dissipation area to the outside air increases, and the heat generated in the stator 51 can be released into the air. As a result, it is possible to improve the heat dissipation characteristics.

The heat pipe 412 opposes the shaft housing 411 in the radial direction over a length equal to or longer than ½ of the axial length L1 of the connection portion 413 between the shaft 41 and the shaft housing 411. As a radially opposing areas of the heat pipe 412 and the shaft housing 411 are longer in the axial direction, the heat transfer area between the shaft 41 and the shaft housing 411 increases, and the heat generated in the stator 51 can be transferred to the shaft housing 411. As a result, it is possible to improve the heat dissipation characteristics.

FIG. 4 is a perspective view of the shaft housing 411 and the impeller 3. A surface extending in the radial direction of the shaft housing 411 includes a concavo-convex portion 4111. The concavo-convex portion 4111 is arranged on an axially upper surface of the shaft housing 411. The concavo-convex portion 4111 is configured such that axially vertical recess and protrusion are alternately arranged in the circumferential direction with the central axis C as the center. According to this configuration, the concavo-convex portion 4111 increases the surface area of the shaft housing 411 and functions as a heat sink. The concavo-convex portion 4111 further functions as a wing so that an air flow on the surface of the shaft housing 411 can be promoted. Therefore, the heat dissipation characteristics can be further improved.

FIG. 5 is a partial longitudinal sectional view of the fan motor 1 according to a first modification. The fan motor 1 according to the first modification includes a shaft 141. The shaft 141 includes a heat pipe 1412 extending in the axial direction. The shaft 141 and the heat pipe 1412 are different members. The heat pipe 1412 is inserted into a hole 1411 provided in the shaft 141. The hole 1411 extends along the central axis C from an axially upper end surface of the shaft 141 to the axially lower side.

Even in the configuration of the first modification, heat generated in the stator 51 is transmitted to the shaft housing 411 via the shaft 141 and the heat pipe 1412. The shaft housing 411 is made of metal and has high thermal conductivity so that heat can be efficiently transmitted to one surface extending in the radial direction, and heat can be efficiently dissipated.

FIG. 6 is a partial longitudinal sectional view of the fan motor 1 according to a second modification. The fan motor 1 according to the second modification includes a filling portion 6. A space between the cover member 52 and the stator 51 inside the cover member 52 is filled with the filling portion 6. In addition, a space between the base portion 53 and the cover member 52 is filled with the filling portion 6. Note that there is also a case where the filling portion 6 is provided without using the cover member 52.

A filling material forming the filling portion 6 is a synthetic resin material, for example, a silicone resin or the like. The filling material forming the filling portion 6 may be a natural resin material such as natural rubber. That is, the stator 51 of the present example embodiment is covered with a resin. More specifically, outer surfaces of the stator core 511, the insulator 512, and the coil 513 are covered with a resin.

In a molded motor in which the stator 51 is covered with the resin, it is difficult to cool the inside of the stator 51. The resin has low thermal conductivity, and hardly releases heat inside the stator 51 to the outside. According to the configuration of the second modification, however, the heat inside the stator 51 can be transmitted to the shaft housing 411 through the shaft 41 and the heat pipe 412 and released to the outside.

FIG. 7 is a partial longitudinal sectional view of the fan motor 1 according to a third modification. The fan motor 1 according to the third modification includes a bearing 156. The bearing 156 is a sleeve bearing. The bearing 156 extends vertically along the axial direction with the central axis C as the center. The bearing 156 extends vertically in the axial direction from the axially lower side of the stator 51 to the axially upper side of the stator 51. That is, the bearing 156 opposes the stator 51 in the radial direction over the entire area in the axial direction of the stator 51.

According to the configuration of the third modification, a contact area between the bearing 156 and the shaft 41 is wider than that in the case of using the ball bearing, and thus, heat of the stator 51 can be efficiently transmitted to the shaft 41. Therefore, it is possible to improve heat dissipation characteristics.

While example embodiments of the present disclosure have been described above, the scope of the present disclosure is not limited thereto, and various modifications can be made without departing from a gist of the disclosure. In addition, features of the above-described example embodiments and the modifications thereof may be combined appropriately as desired.

The present disclosure can be used in, for example, the fan motor.

While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. An outer rotor fan motor comprising: a stator; a shaft that rotates about a central axis extending vertically; a bearing that supports the shaft to be rotatable with respect to the stator; and an impeller that is connected to the shaft via a shaft housing; wherein the shaft includes a heat pipe extending in an axial direction; and the shaft housing is connected to the shaft, extends in a radial direction, and is made of metal.
 2. The fan motor according to claim 1, wherein a diameter of the heat pipe is equal to or longer than about ½ of a diameter of the shaft.
 3. The fan motor according to claim 1, wherein an axial length of a connection portion between the shaft and the shaft housing is longer than a diameter of the shaft.
 4. The fan motor according to claim 1, wherein a diameter of the shaft housing is equal to or longer than twice a diameter of the shaft.
 5. The fan motor according to claim 1, wherein the impeller includes an impeller lid portion that is connected to the shaft housing and extends in the radial direction; and a diameter of the shaft housing is equal to or longer than about ½ of a diameter of the impeller lid portion.
 6. The fan motor according to claim 1, wherein the heat pipe opposes the shaft housing in the radial direction over a length equal to or longer than about ½ of an axial length of the connection portion between the shaft and the shaft housing.
 7. The fan motor according to claim 1, wherein a surface extending in the radial direction of the shaft housing includes a concavo-convex portion.
 8. The fan motor according to claim 1, wherein the stator is covered with a resin.
 9. The fan motor according to claim 1, wherein the bearing is a sleeve bearing. 